Banana peels get a second life as water purifiers. To the surprisingly inventive uses for banana peels — which include polishing silverware, leather shoes, and the leaves of house plants — scientists have added purification of drinking water contaminated with potentially toxic metals. Their report, which concludes that minced banana peel performs better than an array of other purification materials, appears in ACS's journal Industrial & Engineering Chemistry Research.

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Other water purifiers include freshly cut pine tree branches. And nut shells also are recycled. The moral of the story is nothing in nature goes to waste if it can purify something else in nature...or extracts minerals such as copper because banana peals can get out the lead and copper from river water, says a recent study.

Gustavo Castro and colleagues note that mining processes, runoff from farms, and industrial wastes can all put heavy metals, such as lead and copper, into waterways, according to a March 9, 2011 news release, "Banana peels get a second life as water purifier." Heavy metals can have adverse health and environmental effects. Current methods of removing heavy metals from water are expensive, and some substances used in the process are toxic themselves.

Previous work has shown that some plant wastes, such as coconut fibers and peanut shells, can remove these potential toxins from water.

In this report, the researchers wanted to find out whether minced banana peels could also act as water purifiers. The researchers found that minced banana peel could quickly remove lead and copper from river water as well as, or better than, many other materials. A purification apparatus made of banana peels can be used up to 11 times without losing its metal-binding properties, they note. The team adds that banana peels are very attractive as water purifiers because of their low cost and because they don't have to be chemically modified in order to work. The authors acknowledge funding from the São Paulo Research Foundation.

New American Chemical Society podcast: Banana peels purify contaminated water

To the surprisingly inventive uses for banana peels which include polishing silverware, leather shoes, and the leaves of house plants, scientists have added purification of drinking water contaminated with potentially toxic metals. That's the topic of the latest episode in the August 10, 2011 American Chemical Society's (ACS) award-winning "Global Challenges/Chemistry Solutions" podcast series.

It actually points out that minced banana peel performs better than an array of other traditional purification materials. Gustavo Castro and colleagues note in the podcast that mining processes, runoff from farms, and industrial wastes can all put heavy metals, such as lead and copper, into waterways. Heavy metals can have adverse health and environmental effects.

Current methods of removing heavy metals from water are expensive, and some substances used in the process are toxic themselves. Previous work has shown that some plant wastes, such as coconut fibers and peanut shells, can remove these potential toxins from water. The researchers wanted to find out whether minced banana peels could also act as water purifiers.

Researchers discovered that minced banana peel could quickly remove lead and copper from river water as well as, or better than, many other materials

A purification apparatus made of banana peels can be used up to 11 times without losing its metal-binding properties, they note. The team adds that banana peels are very attractive as water purifiers because of their low cost and because they don't have to be chemically modified. The new podcast, based on research published in, appears in ACS's journal Industrial & Engineering Chemistry Research, is available without charge at iTunes and from the ACS Global Challenges site.

Pecan shells recycled

Instead of throwing away organic pecan shells, the waste can be turned into an antimicrobial extract that destroys bacteria on chicken and other organic meats so antibiotics don't have to be used, since you can't use them anyway on certified organic meats and poultry. How the scientists did it began with unroasted and roasted organic pecan shells that were subjected to solvent free extraction to produce antimicrobials that were tested against the bacteria known as Listeria spp. and L. monocytogenes serotypes. You also can see the new study's abstract online, "Efficacy of Antimicrobials Extracted from Organic Pecan Shell for Inhibiting the Growth of Listeria spp." in the November 26, 2013 issue of the Journal of Food Science.

The researchers wanted to find out whether the extract would get rid of the microbes, that is the researchers needed to determine the minimum inhibitory concentrations (MIC) of antimicrobials. When the process worked to satisfaction, then the effectiveness of pecan shell extracts were further tested using a poultry skin model system and the growth inhibition of the Listeria cells adhered onto the skin model were quantified. You also may wish to check out the December 12, 2013 IFT.org news release, "Pecan Shell Extracts May Provide Antimicrobial Option for Preventing Listeria in Organic Meats."

The majority of consumers that eat or buy organic products do not want synthetic antimicrobials or antioxidants added to their foods and prefer a “clean label”. A study in the Journal of Food Science published by the Institute of Food Technologists (IFT) showed that extracts from pecan shells may be effective at protecting meats, such as chicken from listeria growth, explains the IFT's news release.

Unroasted and roasted organic pecan shells were subjected to organic extraction processes to produce antimicrobials that were tested against Listeria spp. and L. monocytogenes bacteria. The effectiveness of pecan shell extracts were further tested using poultry skin to see how much these extracts inhibited bacterial growth of Listeria.

When this all-natural antimicrobial was tested on raw chicken skin it decreased the levels of pathogens by 100 times and at the same time reduced the levels of spoilage organisms by more than 1,000 times, thus greatly increasing the shelf life of the chicken, says the IFT's news release. The researchers concluded that the natural pecan shell extracts may prove to be an effective alternative antimicrobial against food pathogens and supplement the demand for organic antimicrobials.

The solvent free extracts of pecan shells inhibited Listeria strains at MICs as low as 0.38%

The antimicrobial effectiveness tests on a poultry skin model exhibited nearly a 2 log reduction of the inoculated cocktail mix of Listeria strains when extracts of pecan shell powder were used. The extracts also produced greater than a 4 log reduction of the indigenous spoilage bacteria on the chicken skin, noted the study's abstract. So, the pecan shell extracts may prove after all to be very effective alternative antimicrobials against food pathogens and supplement the demand for effective natural antimicrobials for use in organic meat processing. The application is organic and practical.

Pecan shells are a by-product of the shelled pecan industry

By using a novel solvent free extraction system, we have produced antimicrobial compounds from these pecan shells. Antimicrobials from organic pecan shells may be suitable for use in organic meat processing, the study's abstract explains. USDA certified organic meat such as chicken has to qualify before it's certified as organic. That means no antibiotics are to be used.

In order to be certified USDA organic meat, producers are restricted from using antibiotics. In Europe, all antibiotic use in animals is banned. The continued phase-out of antibiotics in all meat production should continue, especially in the US, where antibiotic use is extremely high. In the face of antibiotics, bacteria continue to "outwit" and "out survive" the prescriptions as newer and more dangerous strains form.

With some foods, nothing goes to waste. You can make something out of discarded shells, whether it's flour, antimicrobial extracts, or other uses from fuel to feed to fertilizer. Pecan shells now may be used instead of antibiotics to get rid of bacteria on meats or other foods. The goal, get rid of the bad bacteria while keeping the food organic and healthy so that the humans eating the food are not becoming resistant to antibiotics when they need them. You also may enjoy the article, "How walnuts and flaxseeds may improve your blood pressure and your reaction to stress."

Walnut shells are turned into pellets that burn in stoves. See, "Carbon-negative energy source powers homes on walnut shells video." It's amazing how many uses can be applied to mountains of walnut shells after factories remove and package the walnuts headed to supermarkets, other food stores, restaurants, and school cafeterias. Peach pits also are turned into fuel for cars. Pits, shells, and seeds people throw away from produce is recycled for other uses from fuel to methods of purifying other items from drinking water to foods.

On another note not related to eating walnuts, you may wish to check out the news release, "Cat litter to become an edible product?" Did you know that a freshly-cut pine tree branch can purify certain bacteria from water? (Or does this sound more like a TV ad prelude?)

A small piece of freshly cut sapwood can filter out more than 99 percent of the bacteria E. coli from water, says a new study. The sapwood of pine trees contains xylem, a porous tissue that moves sap from a tree's roots to its top through a system of vessels and pores. It's a natural water filter.

A small piece of freshly cut sapwood can filter out more than 99 percent of the bacteria E. coli from water, In fact, you can use a tree branch to filter your water if the sapwood contains zylem, that porous tissue good for filtering the bacteria out of water. The plant uses the zylem to move sap from the roots to the top of the tree. The new study, "Water Filtration Using Plant Xylem," by authors Boutilier MSH, Lee J, Chambers V, Venkatesh V, and Karnik R was published online today, February 26, 2014 in the journal PLoS ONE. The new study reports that pine tree sapwood filters bacteria from contaminated water.

Researchers were interested in studying low-cost and easy-to-make options for filtering dirty water, a major cause of human mortality in the developing world.

To investigate sapwood's water-filtering potential, researchers collected white pine branches, stripped the outer bark, and cut them into small inch-long sections. They then mounted each in plastic tubing, sealed and secured, and filtered water through that either contained small particles or E. coli bacteria.

The authors found that sapwood filtered out particles greater than 70 nanometers wide, but was unable to separate out 20-nanometer particles, suggesting that there is a particle size limit to what coniferous sapwood can filter. Sapwood also filtered out more than 99% of E. coli from water, which mostly accumulated in the first few millimeters of the wood in what are known as pit membranes.

The small- branch filtration system produced water at rates up to four liters of clean drinking water a day, typically enough for one person.

Be aware, however, that the authors caution only hydrated sapwood (and not dried-out wood) will filter out contaminants. "There's huge variation between plants," says Rohit Karnik, according to the February 26, 2014 news release, "Tree branch filters water." Karnik is senior author on the paper.

"There could be much better plants out there that are suitable for this process. Ideally, a filter would be a thin slice of wood you could use for a few days, then throw it away, and replace at almost no cost. It's orders of magnitude cheaper than the high-end membranes (currently) on the market today, Karnik observes, according to the news release."

This work was supported by the James H. Ferry, Jr. Fund for Innovation in Research Education award to R.K. administered by the Massachusetts Institute of Technology. SEM imaging was performed at the Harvard Center for Nanoscale Systems, a member of the National Nanotechnology Infrastructure Network (NNIN), which is supported by the National Science Foundation under NSF award no. ECS-0335765. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The authors have declared that no competing interests exist. You may also wish to check out the American Society for Microbiology site.

Harvested rainwater harbors pathogens

South Africa has been financing domestic rainwater harvesting tanks in informal low-income settlements and rural areas in five of that nation's nine provinces. But pathogens inhabit such harvested rainwater, potentially posing a public health hazard, especially for children and immunocompromised individuals, according to another study, by different researchers.

The sampling was conducted in the Kleinmond Housing Scheme, which was initiated by the South African Council for Scientific and Industrial Research and the Department of Science and Technology. The houses, designed to be sustainable, are approximately 400 square feet, with alternative technologies such as solar panels and the rainwater tanks.

What kinds of bacteria were found in the harvested rainwater?

The list of predatory prokaryotes the investigators found includes Legionella (found in 73% of samples), Klebsiella (47%) Pseudomonas (19% of samples), Yersinia (28%), Shigella (27%), and others. They also found some protozoan parasites, including Giardia (25% of samples).

Many of the pathogens are normal fresh water inhabitants, but Salmonella (6% of samples) indicates human fecal contamination, while Yersinia are markers of fecal contamination by wild and domestic animals, according to the report.

Residents, many of whom are little-educated and unemployed, typically use the rainwater for washing clothes and house-cleaning, but about one quarter of people polled in the study said they used it for drinking, as well. The finding that coliforms and Escherichia coli counts from rainwater samples—markers of fecal contamination—always significantly exceeded drinking water guidelines, reinforces the World Health Organization's opinion that rainwater must be pretreated prior to use for drinking, says Khan, according to the news release.

Residents often depend on communal 'standpipe' systems

Rainwater harvesting is needed in South Africa's "informal communities" because residents often depend on communal 'standpipe' systems that frequently serve more than 100 people, who may have to walk as far as a third of a mile to get water, says Khan. Approximately 23,000 rainwater tanks have been installed, two thirds of them in the Eastern Cape and one third in KwaZulu Natal. Nearly 20% of South Africans lack sustainable access to water. The final version of the article is scheduled for the April 2014 issue of Applied and Environmental Microbiology.

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Nutrition, health, and media culture writer, Anne Hart is the author of more than 4,000 online articles, 91 paperback books, including numerous novels, and holds a graduate degree in English/creative writing.